Postrelease mortality of spring Chinook Salmon from a mark‐selective recreational fishery in the Yakima River, Washington

Abstract Objective Fishery managers often implement mark‐selective fishing regulations that provide harvest opportunity on abundant hatchery salmon populations while requiring release of at‐risk natural‐origin populations. However, implementing these decisions requires fisheries managers to account for postrelease mortality of any natural‐origin fish caught and released by anglers, which can be variable and is unknown for spring Chinook Salmon Oncorhynchus tshawytscha recreational fisheries in eastern Washington. Therefore, the objective of this study was to estimate and examine the factors affecting, the postrelease mortality of spring Chinook Salmon caught and released from an inland recreational mark–selective fishery in the Yakima River, Washington. Methods We conducted a 2‐year paired control and treatment radio‐telemetry study using 171 treatment fish caught and released during a recreational fishery and 194 control fish captured in a nearby fishway. Subjects were subsequently tracked throughout the summer, and postrelease mortality was estimated on September 1. Stepwise logistic regression was used to analyze potential explanatory variables recorded at the time of capture. Result The estimated postrelease mortality of these fish was 12% (95% CI = 2–23%) just prior to the onset of spawning. We also inferred using logistic regression that anatomical hook location explained most of the variation in mortality rates of angled fish. Conclusion Our estimate of postrelease mortality is similar to estimates derived in other studies for recreational freshwater Chinook Salmon fisheries as well as the current 10% rate used to manage Columbia River spring Chinook Salmon recreational fisheries.